A mechanical-interlock electrical receptacle conducts electricity to an engaged plug, does not conduct electricity when no plug is engaged, and prevents the plug from being disengaged while the receptacle is conducting electricity. The safety features provided by a mechanical-interlock electrical receptacle are critical in industrial or other applications where the current used to power equipment may be 30 to 200 amperes or higher. In these high current applications, a dangerous arc could form between the plug and receptacle if the plug were engaged to, or disengaged from, a powered receptacle.
To prevent arcing, the mechanical-interlock electrical receptacle prevents power from reaching conductors of the receptacle if the plug is not engaged, and prevents a powered plug from being disengaged. To this end, the receptacle may include an interlock mechanism that interacts with an engaged plug. For example, to prevent disengagement of the plug while under electrical load, a receptacle may include a release lever that forces a spring-loaded pin into a slot in the plug to hold the plug in place.
The release lever is connected to a switch that selectively provides power to the receptacle conductors. When no plug is inserted in the receptacle, the release lever is secured in a power-off position. Insertion of a plug into the receptacle permits the release lever to move to a power-on position. This movement of the release lever causes a corresponding movement of the spring-loaded pin, such that the spring-loaded pin is forced into a slot in the plug to secure the plug in the receptacle. To disengage the plug, the release lever is moved to the power-off position, where it locks in place. Movement of the release lever to the power-off position permits the spring-loaded pin to retract from the slot and thereby permits removal of the plug.